Wireless signaling system



Aug. 28, 1%23. 3,455.??52

E. F. W. ALEXANDERSON WIRELESS S IGNALING SYSTEM Original Filed April 19 1916 lnvew'torz Ernst F. W fllexanderson,

His fitter-neg.

ERNST F. N. ,QLEXANDERSOH, Of SCEENECTA'DY, N'EVV YORK, ASSIGNQR TU GENERAL ELECTRIC COTLVEPAI'EY, A GORPGRATION OF Y'ZJRK.

WIRELESS; SIGEALKNG SYSTEM.

firiginal application filed. April 19, 1916, Serial No. 922,155. Divided and this anpliuetio'n filed July 15,

To all whom it may concern Be it known that L ERNST F. VJ. ALEXAN- DICRSON, a. citizen of the United States resid ingat Schenectady, county of Schenectady,

Suite or New York, have invented certain new and useful lmpr veinents in i lireless magnetic wows of varying freguency, which will. in the description which follows be referred to as strays. These Waves are ebsorbed by the receiving antenna and among the variety of waves absorbed there are alvways some which are in rescue-rue that is which have the same length as a signer which is to be received and consequently act, upon the receiving devices in the same way as the signal. Having analyzed this condition both mathematically and experi-- mentally, I have come to the conclusion that a fundamental rule must be the, basis of any device used for decreasing the effect of static disturbances. Any discrimination between a wave of the seine frequency origilisting from stutic and from the signal must be based on some difference in character hetvveen these two waves. if the strays were like the signals both in. frequency and amplitude variation, and in addition to that stronger than the signals there would be no way conceivable fordiscriminsting between one and the other. The longer the period is during which the strays and the Sig sling waves can be compared, the greater is the chance for finding a distiru cunsning dill'erence in the sequence of amplitude ViillfiiiiOHS it nothing else, in order the device he ofl'ectave for discriminaegeinst strays, it should, therefore, be ued so than the wave ins can be dis ished by tempering their character for 'ciently long periods. The receiving devic which 2 1 at present COiDIDeI- ciully are constructed so as to sdvem Serial 1*? e. scenes.

tags of this law to a certain extent by using a highly resonant receiving circuit on which the signal can be allowed to act for a considerable number of successive elternations. The reason why these devices do not entirely discriminate agar st strays is the fact that the receiving antenna. is set in oscillation by static shocks and stray waves of short duration and thus the time during which the disturbances can. act upon the receiving device is prolonged to about the same degree as the signal.

One of the objects of my invention is to provide a means for prolonging" the time during which the signal can act with accumulative etl'ect 'on the receiving device considerably beyond the time during which disturbances can act.

In attaining this object I make use of e tuned circuit of lower then radio frequency, but above audibility for effecting the prolongation of the time during which the signal and disturbances may be compared. The desired lower frequency is provided by means of interference heats between two radio frequencies. Both of these frequencies may be produced at the sending station, or one of theni may be produced at the receiving station. I also provide means for producing. trans-- initting and receiving both radio frequencies. An arrengernent'of this kind is more effective than one employirig a single radio frequency because it is more selective and proof against interference, both frequencies being necessary to produce an impression. in the receiver. vAlso when means is provided at the sendiir; station for establishing the beat frequency a less delicate adjustment of frequency is necessary than when the beat frequency is the result of the difference be tween two high frequencies. A further objcci' of" any invention is to provide means for efiiciently producing signals of the desired character. 1

The features of my invention which I heto he petenteble ere nointcd out with particularity in the appended cl iros. The invention itself, however, together with further objects and advantages thereof, will best be understood by reference to the fol lowing description taken in. connection with the accompanying drawing; in which Figs. 1. 2 end illustrate dii'ierent modifications inc actions are opposite.

of the ciicule ccnue'ctiene which eeemployecl ei eiiemietiug sigeuls'm eceerdience Willi my in'veniueu;

l iese branches connect the windings cf'lwe' magnetic CQHlZX'OllfiZS o3 amplifiers 4 and 5. Each of tlieee crunch circuits include half of the secondary tz'ensfomer 3., the mid.- d e point of which is grounded. The megne tic ccnti'ollei's or amplifiers which I p17eto use in the present case, both as to their construction and method of operaicn, are described in detail in my Letters extent of the Uniiecl States, 1,328,797.

Each controller comprises e reactive Wincllug" consisting of two coils 6 and '7 Wound upon independent magnetic cores 8 and 9., The two cells of each winding are connected in parallel with each other in me circuit and are so arranged that their magnetizing- Eucli magnetic cenecollci is also provided Willi two controlling windings l and 11. wound around the magne'ilcceres S and 9 as N magnetization pl'oducecl by currents in the controlling windings will be in the same clireclion in berth cores. onlrrolling windings 11 are both supplied from llie same source of} cuIlBlll, which in the pi esent case may be en elternecor 12 of much lower frequency than that, of elcernator 1, yet liaving'u froquency above the range of auclibility. Coueroll ng windings are supplied with direct current irom any suitable source, such, loc

example as the direct current generator 13 shown in the drawing. The controlling windings 10 are connected to the generalcr 13 time theii magnetic effects upon the two controllers are opposite with respect to the instantaneous cmgnetic reactions set up in the controllers by current from generator 12. The controllingwindings 10 and 11 are so proportioned and the current sour-es l2 and 13 so chosen and adjusted that the maximum ampere turns of Winding 11 is zipuioxim'lely equal to the ampere turns of comm. conliollci 4- .will have a maximum of controlling ampere turns when the controlling ampere turns of controller 5 are practically zero and vice versa. The cl arecteriscic of inleqpcsee an impedance substantially "elcnl; to an open curcuitun the ccnnectlcn indicated so that 1 ng winding 10. As a result the enciceeion varies jfmm zerc to maximum. Thus when llic'curi'eni Wave of controlling ul ielrimtor 12 is a maximum one of the contljollcl's eels a. short circuic connecting; ue antenna $50 one tei'ininel of the secondary ctrunefoimer 3 While the other contrcller equivto like ozliez' erininel; After the phase of the centrolling current Wave supplied bv ellernctor' 12 is elmngecLlBO electrical dcgices the other controller acts as a shore circuit and the first as an open circuiulhus reversing the polarity the radio frequency current led to the untenne; At inerme (liete points the veltage varies bEtWGQlll-lltiE-Q two extremes in accordance with the sine Wave: law. The current Weve thus supplied tc tlieeutenne has an amplitude pulsationsubetantielly in accordance with the eine Wave law eu-"l the impulses in every other group cf Waves are opposite in phase to corresponding impulses in the interline-(lime giou'lps of Waves. The frequency 0? these uuipitucleflpulsetions is equal "00 the frequency 01" a multiple of the frequency of the ell'ernutoz' 12. For a (lescription in g eetez detail of the operation cf this erz'ungemcm; reference may lie heel lo my United btetes l elcnt 1,380,830.

The wave thus produced in the antenna may be esolved into two waves of constant amplitude, one having alcequency greater than that of the alternator l by an amount equal to the fifequeney of alternator 12 end the olncr having :2, frcquemy us lllllCll lower than that of u'hc alternator 1. l1? either one of glue magnetic 11111)) cm 4; and 5 were used alcne it would lie pos ils-lc to transmit from a single antenna aves of any one of three li'requencies and by providing; multiple {cunlug of the antenna-Waves cf two or more requencics may be transmitted simulc-Lmco'usly. For example, the variable inductance 1 may provide for one tuning and We variable coir denser 15 in shunt to inductance 16 may pr0- Vide for a second tuning at a different "frequency. If, for exemple, alternator 1 has a frequency of 75,000 cycles and alternate: 12., 5000 cycles, the antenna may be tuned for 80,000 and ;000 cycles; 80,000 and 70,000 cycles, or 75,000unc1 70,000 cycles. By pi'0Vi(l--' ing a third curled circuit in multiple we the antenna all three frequencies may be transmitted simultaneously. ll licu both magnetic amplifiers are used in the manner described, the current component of Fumlumental frequency is suppressed and the unlenna, will be tuned for the lwo frequencies into which the resultant Waive may be re solved, that, is, one frequency higher than that of the alternator 1 by an amount equal to the frequency ofthe alternator l2 and the other frequency as much lower than that of the alternator 1. Variable condensers 17 may be connected in series with the windings 6 and 7 of the controllers to neutralize the leakage inductance in the windings thereof so to bring the minimum value of the impedance as near as possible to ashort circuit. It may also be desirable to employ condensers 18 in series with each. branch of the high frequency winding of such a value that they offer very little impedance to the flow of the high frequency current from alternator 1, but a high impedance to currents of the frequency of alternator 12, which may be induced in the closed circuit formed by the two windings 6 and 7.

With the system which has been described above, in order to produce the amplitude pulsations of current, the output delivered by the alternator 1 to the antenna must be periodically varied between a maximum and a minimum. As a result the energy outputwhich can be obtained from the alternator is less than it would be if it delivered full power continuously. To overcome this disadvantage an oscillating circuit may be pro vided which is capable of storing up considerably more energy than the alternator must give out during one period of the amplitude pulsations. By this means energy may be stored up in the oscillating circuit when the energy taken by the antenna is a minimum and when the energy taken by the antenna is a maximum energy may be drawn niomentarily from the oscillating circuit at a greater rate than the alternator is able to deliver. In the present case the oscillating energy storage circuit may be made up of the primary of transformer 3 and condenser 19.

In order to transmit telegraphic signals by the system described a key 20 may be inserted in the circuit of alternator 12. When this key is open the impedance of the two con- (rollers 4 and 5 will be equal and since they are connected in opposition to each other no current will be supplied to the antenna. When the key is closed currents having amplitude pulsations will be supplied to the antenna in the manner described. I

In Fig. 2 I have shown an organization in which a single magnetic controller 21 is em ployed to secure the desired frequency split-- ting. In this case a single controlling winding 22 is shown and the alternator 12 is connected tothe winding in series with a battery 23 having a potential substantially he same as that of alternator 12. The controlling windings 6 and? of this controller are connectedin shunt to the se ondary of trans former 3 instead of in series as in the rangement shown in Fig. 1. An oscillating energy storage circuit comprising inductance 23 i and condenser 25 connected in shunt to In Fig. 3 I have illustrated another modi fication in which the circuit which provides the second tuning for the antenna is also utilized as an energy storage circuit. Controller 5 in thistcase is connected in series with the antehnaand controller at in a circuit in shunt to the secondary or transformer '3. The main antenna tuning is made by means of variable inductance and the second tuning by variable condenser 31. This condenser in connection with inductances 32 forms an energy storage circuit. when controller a forms a short circuit if the phase relations of the currents are properly adjusted energy will be deliveredto the storage circuit by means of transformer 33 and when controller 5 forms a short circuit energy will be delivered to the antenna from the alternator and the storage circuit.

l i hile l have indicated only three. dif ferent circuit arrangements whereby my in vention may be carried into efi'ect it will be apparent that many modifications may be made in the specific apparatus and the manner in which it is employed without departing from the scope of my invention as set forth iii the appended claims. v

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. The method of producing an electric current wave of radio frequency having amplitude pulsations in which the impulses of alternate amplitude pulsations are opposite in phase to corresponding impulses of intermediate amplitude pulsations which consists in continuously delivering current from a source of radio t'rcquency to a suitable electric circuit varying the amplitudes of the impulses of current thu delivered, periodically IG;*8ISll1g with respect to said source and with frequency corresponding to the desired frequency of the amplitude pulsations of the wave, the direction of current; flow in the circuitstoring up energy from the current source in a second resonant circuit when the amplitude of the current delivered is smaller than that which the source capable of delivering normally, and delivering the store-l up energy to the first circuit when the amplitude ot the current flowing therein increases beyond. that mor mally furnished by the current source.

2. The method of producing an electric current wave which is the equivalent of two electric current waves of different frequencies and or constant amplitudes which consists iu costinuously supplying current from the current delivered to the first circuit is i smaller than that "which the source is capable of deliverin normally, and delivering this storcd'up energy to the first circuit when the amplitude of the current flowing therein increases beyond that normally furnished by the current source.

3. The method of transmitting signals which consists in producing currents of two diliicrent radio frequencies from a single source of current of radioirequency first producingfrom said source 21 currcntjhcv ng amplitude pulsations of uniform character in which corresponding impulses of uni; two adjacent groupsof amplitude pulsations arc opposite in phase and-then conducting;- the current thus produced through a circuit haw ic zm branches which are resonant to the arm requcncics desired whereby the current i is resolved into two currents of con- ,mplitudc and the frequencies and utilizing the two currents thus produced for'the tr'onsmission of signals. 4

i, The method of transmitting si usls which consists in. producin currents or different rudio frequencies from as single source of current of radio frequency by delivering currentv from said source to a suitable electric circuit, uniformly varying the amplitudes of the impulses of current thus delivered to produce, u current Wave having amplitude pulsations 0)? s lower fro quency than that of the source shove audibility, and then conducting the current thus produced through a circuit having two branches which are resonant to the two frcquencies desired wherchy tho current wave Will he resolved into two currents of cow stout amplitude and of the frequencies deand utilizing the two currents thus produced for the transmission 'o'l' signals.

5. The niethodot producing currents of two different frequencies from single source of current of radio frequency which consists in. dclivcring current from. said source to a suitable electric circuit, uniformly varying: the amplitude of the rim-- puls'cs of current thus delivcrcd to produce a current wave having amplitude pulsations of a lower frcqucncy than that of the source but above audihility, storing up energy from the current source in a second resonuuhcircuit when the amplitude of the currcntds livcred is smaller than that which the source amplitude pulsotious of tho is cupublc of delivering normoliy, delivcn ingthc stored up energy to the firstcircuis When'thc amplitude of the. current flowing therein increases beyond that normally fun electric circuit connected thereto, me for vsryiw g; the amplitudes of the impulses. of currcnt'dclivercd to said circuit, means periodically reversing with respect to currentsource sud with corresponding to the: desired frequency oi the issue, the di motion of current .llow in circuit. second res-count circuit associated with the first circuit for storing u energy irom the con rent source when no. current domin in the first circuit is smaller than that which the source iscupsble of delivcring and delivering energy to the circuit When-tho amplitude of the currcnt flowing therein iucrsusss beyond that norhiciiy fur rushed hy the current sourco 7. Means for producing on ul'sctrio cur--- c uivalcnt or two rent Wave which is the electric current Waves oioifiurcht lircqucncies and or" constun sinplisudcs, compris ing a source of continuous cucrcul; of radio frequency, on electric circuit ossociutcd therewith, mucus for uniformly varying the amplitudes of the pulsctions supplied to said circuit in such o way as to produce u current wave with regularly recurring amplitude pulsations, and as second resonant circuit ussocistc'd with the. first circuit for storing up energy from the current source when the amplitude of the current delivcrcd therefrom to the first circuit is smaller ihoh that which the sourcc is capable of dciivcr ing normally, and delivering" energy to the first circuit when the amplitude? the current flowing therein isgrester than that nor mally furnished by 'thccgxrreht source.

8. Means for transmitting signals con;-

-prising means for producing currents of two different frequencies comprising a single source of current of radio frequency, on electric circuit associated therewith, means for deliver-in to said'circuit a current having amplitude pulsations of uniform character in which corresponding impulses of any two adjacent amplitude puisstions are opposite in phase, said electric cir- Ell cuit having two branches which are resonant to the two frequencies desired whereby the current furnished thereto may be resolved into two currents of constant amplitude and of the frequenciesdesired and means for utilizing said currents for the transmission of signals.

9. Means for transmitting signals comprising means for producing currents of two different radio frequencies comprising a single source of current of radio frequency, an electric circuit associated therewith, means for uniformly varying the amplitudes of the impulses of current delivered to said circuit to produce a current wave having amplitude pulsations of a lower frequenc than that of the source but above audibility, said circuit comprising two branches which are resonant to the two frequencies desired whereby the current Wave stant amplitude of the frequencies desired and means for utilizing currents thus produced for the transmission of signals.

10. Means for producing currents of two different radio frequencies comprising a single source of current of radio frequency, an electric circuitassociated therewith, means for uniformly varying the amplitudes of the impulses of current delivered to said circuit to produce a current wave having amplitude pulsations of a lower fre quency than that of the source but above audibility, said circuit comprising two branches which are resonant to the two frequencies desired, whereby the current wave may be resolved into two-currents of constant amplitude and of the frequencies desired, and a second circuit associated with the first which is resonant to the frequency of the current source for storing up energy from said source when the amplitude of the current delivered is smaller than that which the source is capable of deliverin norm-ally, and delivering energy to the rst circuit when the amplitude of the current flowing therein increases beyond that normally furnished by the current source.

11. The combination in a system for transmitting signals of a source of high frequency current, an electric circuit associated therewith, a source of controlling current of lower frequency than the first mentioned source, means for alternately diverting by means of said controlling current the effective path for the flow of current in said trollin may be resolved into two currents of concircuit from one terminal of said source to the other terminal thereof at a frequency corresponding to the frequency of said controlling current, and a signaling device in circuit with said source of controlling current. v

12. The combination in a system for transmitting signals of a source of high frequency current, an electric circuit asso ciated with said source, a source of controlling current associated therewith of lower frequency than the first mentioned source, electromagnetic means operatively related to said circuit and operable by means of said controlling current for changing the effective path for the flow of current in said circuit from one terminal of said source to the other terminal thereof, and a signaling device in circuit with said source of concurrent.

13. he combination in a system for transmitting signals of a source of high frequency current, an electric circuit ineluding two parallel pathsdt'or the How of current, said two parallel paths being electrically associated at one end with opposite terminals of said source and electrically connected together at the opposite end, a source of controlling current of lower frequency than the first mentioned source means for varying the impedance of said parallel paths in accordance with variations in said controlling current and a signaling device in circuit with said source of controlling current.

14-. The combination in a. system for transmitting signals of a source of high frequency current, an electric circuit including two parallel paths for the flow of current. said two parallel paths being electrically associated at one end with opposite. terminals of said source and electrically connected together at the opposite end, a

source of controlling current of lower frequency than the first mentioned source, a magnetic controller associated with each of said parallel paths, means for varying the impedance of each of said magnetic controllers in accordance with variations in said controlling current, and a signaling device in circuit with said source of controlling current.

In witness whereof, I have hereunto set my hand this 13th day of July, 1918.

ERNST F. W. ALEXANDERSON., 

